[14] RFR: JDK-8193911: Create README file to document bumping the version number

[Kevin Rushforth]

Ambarish and Johan,

Please review the following to add instructions for bumping the JavaFX 
release version number:

https://bugs.openjdk.java.net/browse/JDK-8193911
https://github.com/javafxports/openjdk-jfx/pull/527

Thanks.

-- Kevin